Optical imaging system

Abstract

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side. The first lens has a positive refractive power, and the second lens has a negative refractive power. The refractive index of the second lens is greater than the refractive index of each of the first and third lenses. The optical imaging system satisfies TTL / (2×IMG HT) < 0.6 and 0 < f1 / f < 1.4, where TTL is the distance along the optical axis from the object-side surface of the first lens to the imaging plane, IMG HT is half the diagonal length of the imaging plane, f is the total focal length of the optical imaging system, and f1 is the focal length of the first lens.

Description

Optical Imaging System [Cross - Reference to Related Applications] This application claims the priority benefit of Korean Patent Application No. 10 - 2022 - 0115737, filed with the Korean Intellectual Property Office on September 14, 2022. The entire disclosure of the Korean patent application is incorporated herein by reference for all purposes. The following description relates to an optical imaging system. Recent portable terminals may include a camera provided with an optical imaging system, and the optical imaging system includes multiple lenses to perform video calls and capture images. As the functions of cameras in portable terminals have gradually increased, the demand for high - resolution cameras for portable terminals has also increased. In particular, in recent years, image sensors with a high pixel count (e.g., 13 million pixels to 100 million pixels) have been adopted in cameras for portable terminals to implement clearer image quality. That is, the size of the image sensor has increased, and thus the total length of the optical imaging system has also increased, such that there may be a problem of the camera protruding from the portable terminal. In addition, since portable terminals have been designed to have a smaller size, and cameras for portable terminals also need to have a reduced size, it is necessary to develop an optical imaging system with a thin size and high resolution. This invention content is provided to introduce in a simplified form a series of concepts further described in the embodiments below. This invention content is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter. In one general aspect, an optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens sequentially arranged from the object side. The first lens has a positive refractive power, and the second lens has a negative refractive power. The refractive index of the second lens is greater than the refractive index of each of the first lens and the third lens. The optical imaging system satisfies TTL / (2×IMG HT) < 0.6 and 0 < f1 / f < 1.4, where TTL is the distance on the optical axis from the object - side surface of the first lens to the imaging plane, IMG HT is half of the diagonal length of the imaging plane, f is the total focal length of the optical imaging system, and f1 is the focal length of the first lens. Among the first lens to the eighth lens, at least three lenses including the second lens may have a refractive index greater than 1.61, and among the at least three lenses with a refractive index greater than 1.61, the absolute value of the focal length of the second lens may be the smallest. It can satisfy at least one of the following: 25 < v1 - v2 < 45, v1 - v4 < 45, and 10 < v1 - (v6 + v7) / 2 < 30, where v1 is the Abbe number of the first lens, v2 is the Abbe number of the second lens, v4 is the Abbe number of the fourth lens, v6 is the Abbe number of the sixth lens, and v7 is the Abbe number of the seventh lens. The second lens, the fifth lens, and the sixth lens can have a refractive index greater than 1.61 and can satisfy 60 < v2 + v5 + v6 < 80, where v2 is the Abbe number of the second lens, v5 is the Abbe number of the fifth lens, and v6 is the Abbe number of the sixth lens. The fifth lens can have a negative refractive power, and each of the second lens and the fifth lens can have a refractive index greater than 1.66. The optical imaging system can satisfy -10 < f2 / f < -1; 1 < |f3 / f|; and 3 < |f4 / f|, where f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens. The optical imaging system can satisfy -0.6 < f1 / f2 < 0. The optical imaging system can satisfy -0.1 < f1 / f3 < 1. The optical imaging system can satisfy 0 < |f2 / f3| < 1. The optical imaging system can satisfy 1.5 < f34 / f < 5.5, where f34 is the combined focal length of the third lens and the fourth lens. The optical imaging system can satisfy at least one of the following: 3 < |f5 / f|; 1 < |f6 / f|; 0 < f7 / f < 2; and -1 < f8 / f < 0, where f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens. The optical imaging system can satisfy TTL / f < 1.3 and BFL / f < 0.3, where BFL is the distance on the optical axis from the image-side surface of the eighth lens to the imaging plane. The optical imaging system can satisfy 0 < D1 / f < 0.1, where D1 is the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens. The optical imaging system can satisfy 0 < D3 / f < 0.2, where D3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens. The optical imaging system can satisfy 70° < FOV × (IMG HT / f), where FOV is the field of view of the optical imaging system. The fourth lens may have a positive refractive power, the fifth lens may have a negative refractive power, the seventh lens may have a positive refractive power, and the eighth lens may have a negative refractive power. Other features and aspects will become apparent by reading the following detailed description, the drawings, and the claims. The following detailed description is provided to assist the reader in obtaining a comprehensive understanding of the methods, apparatuses, and / or systems described herein. However, various changes, modifications, and equivalent forms of the methods, apparatuses, and / or systems described herein will be apparent to those of ordinary skill in the art. The order of operations described herein is merely an example and is not intended to limit the order of operations set forth herein, but rather may be changed, as will be apparent to those of ordinary skill in the art, except for operations that must be performed in a particular order. In addition, descriptions of functions and structures well known to those of ordinary skill in the art may be omitted for increased clarity and conciseness. The features described herein may be implemented in different forms and are not to be construed as limited to the examples described herein. Rather, the examples described herein are provided so that this disclosure will be thorough and complete and will fully convey the scope of this disclosure to those of ordinary skill in the art. Note that, herein, the term "may" with respect to an example or embodiment (e.g., with respect to what an example or embodiment may include or implement) means that there is at least one example or embodiment that includes or implements such a feature, and all examples and embodiments are not limited thereto. Throughout the specification, when an element such as a layer, region, or substrate is described as being "on," "connected to," or "coupled to" another element, the element may be directly "on," directly "connected to," or directly "coupled to" the other element, or there may be one or more other elements therebetween. Conversely, when an element is described as being "directly on," "directly connected to," or "directly coupled to" another element, there may be no other elements therebetween. The term "and / or" as used herein includes any one and any combination of any two or more of the associated listed items. Although terms such as "first," "second," and "third" may be used herein to describe various components, elements, regions, layers, or sections, such components, elements, regions, layers, or sections are not limited by these terms. Rather, these terms are only used to distinguish one component, element, region, layer, or section from another. Thus, a first component, element, region, layer, or section referred to in the examples described herein may also be referred to as a second component, element, region, layer, or section without departing from the teachings of the examples. For ease of explanation, spatially relative terms such as "above", "upper", "below", and "lower" may be used herein to describe the relationship of one element shown in the figures to another element. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, an element described as "above" or "upper" relative to another element will then be "below" or "lower" relative to the other element. Thus, the term "above" encompasses both the above and below orientations depending on the spatial orientation of the device. The device may be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatially relative terms used herein are to be interpreted accordingly. The terms used herein are for the purpose of describing various examples only and are not intended to limit the disclosure. Unless the context clearly dictates otherwise, the articles "a", "an", and "the" are intended to include the plural forms as well. The terms "comprises", "includes", and "has" specify the presence of the stated features, numbers, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, components, elements, and / or combinations thereof. Due to manufacturing techniques and / or tolerances, the shapes shown in the figures may vary. Accordingly, the examples described herein are not limited to the specific shapes shown in the figures but include shape variations that occur during manufacturing. As will be apparent after understanding the disclosure of the present application, the features of the examples described herein can be combined in various ways. In addition, although the examples described herein have various configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application. The figures may not be drawn to scale, and for clarity, illustration, and convenience, the relative sizes, proportions, and depiction of elements in the figures may be exaggerated. In the figures showing the lens, the thickness, size, and shape of the lens are exaggerated to show the examples, and the spherical or aspherical shape of the lens shown in the figures is an example and the shape is not limited thereto. The first lens refers to the lens closest to the object side, and the eighth lens refers to the lens closest to the imaging plane (or image sensor). In addition, in each lens, the first surface refers to the surface adjacent to the object side (or object-side surface), and the second surface refers to the surface adjacent to the image side (or image-side surface). In addition, in each example, the unit of numerical values such as the radius of curvature, thickness, distance, focal length, etc. of the lens is millimeters, and the unit of the field of view (FOV) is degrees. In addition, in the description of the shape of each lens, the concept that a surface is convex indicates that the paraxial region of the surface is convex, the concept that a surface is concave indicates that the paraxial region of the surface is concave, and the concept that a surface is flat indicates that the paraxial region of the surface is flat. Therefore, even when it is stated that a surface of a lens is convex, the edge portion of the lens may be concave. Similarly, even when it is stated that a surface of a lens is concave, the edge portion of the lens may be convex. In addition, when it is stated that a surface of a lens is flat, the edge portion of the lens may be convex or concave. The paraxial region refers to a relatively narrow region adjacent to the optical axis. The imaging plane may refer to a virtual plane on which a focus can be formed by an optical imaging system. As an alternative, the imaging plane may refer to a surface of an image sensor on which light is received. The optical imaging systems in various examples may include eight lenses. For example, the optical imaging system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens sequentially arranged from the object side. The first lens to the eighth lens may be spaced apart from each other by a predetermined distance along the optical axis. However, the optical imaging system may not include only eight lenses, and if necessary, may further include other components. For example, the optical imaging system may further include an image sensor for converting an incident image of an object into an electrical signal. In addition, the optical imaging system may further include an infrared filter (hereinafter referred to as a "filter") for blocking infrared rays. The filter may be disposed between the eighth lens and the image sensor. In addition, the optical imaging system may further include a stop for adjusting the amount of incident light. The first lens to the eighth lens included in the optical imaging system may be formed of a plastic material. In addition, at least one of the first lens to the eighth lens has an aspherical surface. In addition, each of the first lens to the eighth lens may have at least one aspherical surface. That is, at least one of the first surface and the second surface of the first lens to the eighth lens may be aspherical. Here, the aspherical surfaces of the first lens to the eighth lens are represented by Equation 1. [Equation 1] In Equation 1, c is the curvature of the lens (the reciprocal of the radius of curvature), K is the conic constant, and Y is the distance from a point on the aspherical surface of the lens to the optical axis. In addition, the constants A to P refer to aspherical coefficients. Z is the distance in the optical axis direction between a point on the aspherical surface of the lens and the vertex of the aspherical surface. The optical imaging systems in various examples can satisfy at least one of the following conditional expressions: [Conditional Expression 1] 0 < f1 / f < 1.5 [Conditional Expression 2] 25 < v1 - v2 < 45 [Conditional Expression 3] 25 < v1 - v4 < 45 [Conditional Expression 4] 0 ≤ v1 - v6 < 25 [Conditional Expression 5] -5 < f2 / f < -1 [Conditional Expression 6] -10 < f3 / f / 100 < 2 [Conditional Expression 7] -5 < f4 / f / 100 < 1 [Conditional Expression 8] -3 < f5 / f / 100 < 3 [Conditional Expression 9] -50 < f6 / f < 10 [Conditional Expression 10] -5 < f7 / f < 0 [Conditional Expression 11] TTL / f < 1.3 [Conditional Expression 12] -0.5 < f1 / f2 < 0 [Conditional Expression 13] -1 < f1 / f3 < 3 [Conditional Expression 14] BFL / f < 0.3 [Conditional Expression 15] D1 / f < 0.1 [Conditional Expression 16] TTL / (2×IMG HT) < 0.62 [Conditional Expression 17] 70° < FOV×(IMG HT / f) [Conditional Expression 18] 1.5 < f / EPD < 2.3 [Conditional Expression 19] 2 < CT1 / ET1 < 5 [Conditional Expression 20] |f1 / f2 / n2| < 0.3 [Conditional Expression 21] |f1 / f4 / n4| < 0.3 [Conditional Expression 22] SWA71 < 30° [Conditional Expression 23] SWA72 < 42° [Conditional Expression 24] v2 + v4 < v3 [Conditional Expression 25] v2 + v4 < v1 [Conditional Expression 26] 4.9 < n2 + n4 + n5 < 5.2 In the conditional expressions, f is the total focal length of the optical imaging system, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, f8 is the focal length of the eighth lens, and f34 is the combined focal length of the third lens and the fourth lens. In the conditional expressions, v1 is the Abbe number of the first lens, v2 is the Abbe number of the second lens, v3 is the Abbe number of the third lens, v4 is the Abbe number of the fourth lens, v5 is the Abbe number of the fifth lens, v6 is the Abbe number of the sixth lens, and v7 is the Abbe number of the seventh lens. In the conditional expression, TTL is the distance on the optical axis from the object-side surface of the first lens to the imaging plane, BFL is the distance on the optical axis from the image-side surface of the eighth lens to the imaging plane, D1 is the distance on the optical axis between the image-side surface of the first lens and the object-side surface of the second lens, and D3 is the distance on the optical axis between the image-side surface of the third lens and the object-side surface of the fourth lens. In the conditional expression, IMG HT is half of the diagonal length of the imaging plane, and FOV is the field of view of the optical imaging system. The first lens may have a positive refractive power. In addition, the first lens may have a meniscus shape that bulges toward the object. More specifically, the first surface of the first lens may be convex, and the second surface of the first lens may be concave. At least one of the first surface and the second surface of the first lens may be aspherical. For example, both surfaces of the first lens may be aspherical. The second lens may have a negative refractive power. In addition, the second lens may have a meniscus shape that bulges toward the object side. More specifically, the first surface of the second lens may be convex, and the second surface of the second lens may be concave. At least one of the first surface and the second surface of the second lens may be aspherical. For example, both surfaces of the second lens may be aspherical. The third lens may have a positive refractive power or a negative refractive power. In addition, the third lens may have a meniscus shape that bulges toward the object. More specifically, the first surface of the third lens may be convex, and the second surface of the third lens may be concave. At least one of the first surface and the second surface of the third lens may be aspherical. For example, both surfaces of the third lens may be aspherical. The fourth lens may have a negative refractive power. In addition, the fourth lens may have a meniscus shape that bulges toward the object side. More specifically, the first surface of the fourth lens may be concave, and the second surface of the fourth lens may be convex. As an alternative, the fourth lens may have a meniscus shape that bulges toward the image side. More specifically, the first surface of the fourth lens may be convex, and the second surface of the fourth lens may be concave. As an alternative, both surfaces of the fourth lens may be convex. More specifically, both the first surface and the second surface of the fourth lens may be convex. At least one of the first surface and the second surface of the fourth lens may be aspherical. For example, both surfaces of the fourth lens may be aspherical. The fifth lens may have a negative refractive power. In addition, the fifth lens may have a meniscus shape convex toward the object. More specifically, the first surface of the fifth lens may be convex in the paraxial region, while the second surface of the fifth lens may be concave in the paraxial region. As an alternative, the fifth lens may have a meniscus shape convex toward the image. More specifically, the first surface of the fifth lens may be concave, while the second surface of the fifth lens may be convex. As an alternative, both surfaces of the fifth lens may be concave. More specifically, both the first surface and the second surface of the fifth lens may be concave. At least one of the first surface and the second surface of the fifth lens may be aspherical. For example, both surfaces of the fifth lens may be aspherical. The sixth lens may have a positive refractive power or a negative refractive power. In addition, the sixth lens may have a meniscus shape convex toward the object side. More specifically, the first surface of the sixth lens may be convex in the paraxial region, while the second surface of the sixth lens may be concave in the paraxial region. At least one of the first surface and the second surface of the sixth lens may be aspherical. For example, both surfaces of the sixth lens may be aspherical. The sixth lens may have at least one inflection point formed on at least one of the first surface and the second surface. For example, the first surface of the sixth lens may be convex in the paraxial region and concave in portions other than the paraxial region. The second surface of the sixth lens may be concave in the paraxial region and convex in portions other than the paraxial region. The seventh lens may have a positive refractive power. In addition, the seventh lens may have a meniscus shape convex toward the object side. More specifically, the first surface of the seventh lens may be convex in the paraxial region, while the second surface of the seventh lens may be concave in the paraxial region. As an alternative, both surfaces of the seventh lens may be convex. More specifically, both the first surface and the second surface of the seventh lens may be convex. At least one of the first surface and the second surface of the seventh lens may be aspherical. For example, both surfaces of the seventh lens may be aspherical. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens. For example, the first surface of the seventh lens may be convex in the paraxial region and concave in portions other than the paraxial region. The second surface of the seventh lens may be concave in the paraxial region and convex in portions other than the paraxial region. The eighth lens may have a negative refractive power. In addition, the eighth lens may have a meniscus shape that bulges toward the object side surface. More specifically, the first surface of the eighth lens may be convex in the paraxial region, while the second surface of the eighth lens may be concave in the paraxial region. As another alternative, both surfaces of the eighth lens may be concave. More specifically, both the first surface and the second surface of the eighth lens may be concave. At least one of the first surface and the second surface of the eighth lens may be aspherical. For example, both surfaces of the eighth lens may be aspherical. In addition, in the eighth lens, at least one inflection point may be formed on at least one of the first surface and the second surface. For example, the first surface of the eighth lens may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the eighth lens may be concave in the paraxial region and convex in a portion other than the paraxial region. Each of the first lens to the third lens may be configured to have a refractive index different from that of an adjacent lens. For example, the first lens and the second lens have different refractive indices, and the second lens and the third lens may have different refractive indices. In addition, among the first lens to the third lens, the refractive index of the second lens may be the largest. At least three lenses including the second lens among the first lens to the eighth lens may have a refractive index greater than 1.61. For example, the refractive index of the second lens, the refractive index of the fifth lens, and the refractive index of the sixth lens may be greater than 1.61. In addition, the refractive index of the second lens and the refractive index of the fifth lens may be greater than 1.66. Among the lenses with a refractive index greater than 1.61, the absolute value of the focal length of the second lens may be the lowest. The optical imaging system 100 according to the first example will be described with reference to FIGS. 1 and 2. The optical imaging system 100 may include an optical system including a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, and may further include a filter 190 and an image sensor IS. The optical imaging system 100 may form a focal point on the imaging plane 191. The imaging plane 191 may refer to a surface on which the optical imaging system can form a focal point. For example, the imaging plane 191 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 1. [Table 1] The total focal length f of the optical imaging system 100 can be 6.3132 mm, the IMG HT can be 6.12 mm, and the FOV can be 85.3°. In the first example, the first lens 110 can have a positive refractive power, the first surface of the first lens 110 can be convex, and the second surface of the first lens 110 can be concave. The second lens 120 can have a negative refractive power, the first surface of the second lens 120 can be convex, and the second surface of the second lens 120 can be concave. The third lens 130 can have a negative refractive power, the first surface of the third lens 130 can be convex, and the second surface of the third lens 130 can be concave. The fourth lens 140 can have a positive refractive power, the first surface of the fourth lens 140 can be concave, and the second surface of the fourth lens 140 can be convex. The fifth lens 150 can have a negative refractive power, the first surface of the fifth lens 150 can be concave, and the second surface of the fifth lens 150 can be convex. The sixth lens 160 can have a negative refractive power, the first surface of the sixth lens 160 can be convex in the paraxial region, and the second surface of the sixth lens 160 can be concave in the paraxial region. In addition, at least one inflection point can be formed on at least one of the first surface and the second surface of the sixth lens 160. For example, the first surface of the sixth lens 160 can be convex in the paraxial region and concave in the portion other than the paraxial region. In addition, the second surface of the sixth lens 160 can be concave in the paraxial region and convex in the portion other than the paraxial region. The seventh lens 170 can have a positive refractive power, the first surface of the seventh lens 170 can be convex in the paraxial region, and the second surface of the seventh lens 170 can be concave in the paraxial region. In addition, at least one inflection point can be formed on at least one of the first surface and the second surface of the seventh lens 170. For example, the first surface of the seventh lens 170 can be convex in the paraxial region and concave in the portion other than the paraxial region. In addition, the second surface of the seventh lens 170 can be concave in the paraxial region and convex in the portion other than the paraxial region. The eighth lens 180 can have a negative refractive power, the first surface of the eighth lens 180 can be convex in the paraxial region, and the second surface of the eighth lens 180 can be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 180. For example, the first surface of the eighth lens 180 may be convex in the paraxial region and concave in a portion other than the paraxial region. In addition, the second surface of the eighth lens 180 may be concave in the paraxial region and convex in a portion other than the paraxial region. Each surface of the first lens 110 to the eighth lens 180 may have an aspherical coefficient as shown in Table 2. For example, both the object-side surface and the image-side surface of the first lens 110 to the eighth lens 180 may be aspherical. [Table 2] In addition, the optical imaging system 100 may have the aberration characteristics shown in FIG. 2. The optical imaging system 200 according to the second example will be described with reference to FIGS. 3 and 4. The optical imaging system 200 may include an optical system including a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, a seventh lens 270, and an eighth lens 280, and may further include a filter 290 and an image sensor IS. The optical imaging system 200 may form a focal point on the imaging plane 291. The imaging plane 291 may refer to a surface on which the optical imaging system can form a focal point. For example, the imaging plane 291 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 3. [Table 3] The total focal length f of the optical imaging system 200 may be 6.3083 mm, IMG HT may be 6.12 mm, and FOV may be 85.3°. In the second example, the first lens 210 may have a positive refractive power, the first surface of the first lens 210 may be convex, and the second surface of the first lens 210 may be concave. The second lens 220 may have a negative refractive power, the first surface of the second lens 220 may be convex, and the second surface of the second lens 220 may be concave. The third lens 230 may have a positive refractive power, the first surface of the third lens 230 may be convex, and the second surface of the third lens 230 may be concave. The fourth lens 240 may have a positive refractive power, the first surface of the fourth lens 240 may be concave, and the second surface of the fourth lens 240 may be convex. The fifth lens 250 may have a negative refractive power. The first surface of the fifth lens 250 may be convex, and the second surface of the fifth lens 250 may be concave. The sixth lens 260 may have a negative refractive power. The first surface of the sixth lens 260 may be convex in the paraxial region, and the second surface of the sixth lens 260 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 260. For example, the first surface of the sixth lens 260 may be convex in the paraxial region and concave in a portion other than the paraxial region. In addition, the second surface of the sixth lens 260 may be concave in the paraxial region and convex in a portion other than the paraxial region. The seventh lens 270 may have a positive refractive power. The first surface of the seventh lens 270 may be convex in the paraxial region, and the second surface of the seventh lens 270 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 270. For example, the first surface of the seventh lens 270 may be convex in the paraxial region and concave in a portion other than the paraxial region. In addition, the second surface of the seventh lens 270 may be concave in the paraxial region and convex in a portion other than the paraxial region. The eighth lens 280 may have a negative refractive power. The first surface of the eighth lens 280 may be convex in the paraxial region, and the second surface of the eighth lens 280 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 280. For example, the first surface of the eighth lens 280 may be convex in the paraxial region and concave in a portion other than the paraxial region. In addition, the second surface of the eighth lens 280 may be concave in the paraxial region and convex in a portion other than the paraxial region. Each surface of the first lens 210 to the eighth lens 280 may have an aspherical coefficient as shown in Table 4. For example, both the object-side surface and the image-side surface of the first lens 210 to the eighth lens 280 may be aspherical. [Table 4] In addition, the optical imaging system 200 may have the aberration characteristics shown in FIG. 4. The optical imaging system 300 according to the third embodiment will be described with reference to FIGS. 5 and 6. The optical imaging system 300 may include an optical system including a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, a sixth lens 360, a seventh lens 370, and an eighth lens 380, and may further include a filter 390 and an image sensor IS. The optical imaging system 300 may form a focus on the imaging plane 391. The imaging plane 391 may refer to a surface on which the optical imaging system can form a focus. For example, the imaging plane 391 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 5. [Table 5] The total focal length f of the optical imaging system 300 may be 6.2878 mm, the IMG HT may be 6.12 mm, and the FOV may be 85.3°. In the third example, the first lens 310 may have a positive refractive power, the first surface of the first lens 310 may be convex, and the second surface of the first lens 310 may be concave. The second lens 320 may have a negative refractive power, the first surface of the second lens 320 may be convex, and the second surface of the second lens 320 may be concave. The third lens 330 may have a positive refractive power, the first surface of the third lens 330 may be convex, and the second surface of the third lens 330 may be concave. The fourth lens 340 may have a positive refractive power, the first surface of the fourth lens 340 may be concave, and the second surface of the fourth lens 340 may be convex. The fifth lens 350 may have a negative refractive power, the first surface of the fifth lens 350 may be convex, and the second surface of the fifth lens 350 may be concave. The sixth lens 360 may have a negative refractive power, the first surface of the sixth lens 360 may be convex in the paraxial region, and the second surface of the sixth lens 360 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 360. For example, the first surface of the sixth lens 360 may be convex in the paraxial region and concave in a portion other than the paraxial region. In addition, the second surface of the sixth lens 360 may be concave in the paraxial region and convex in a portion other than the paraxial region. The seventh lens 370 may have a positive refractive power, the first surface of the seventh lens 370 may be convex in the paraxial region, and the second surface of the seventh lens 370 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 370. For example, the first surface of the seventh lens 370 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the seventh lens 370 may be concave in the paraxial region and convex in a portion other than the paraxial region. The eighth lens 380 may have a negative refractive power. The first surface of the eighth lens 380 may be convex, and the second surface of the eighth lens 380 may be concave. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 380. For example, the first surface of the eighth lens 380 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the eighth lens 380 may be concave in the paraxial region and convex in a portion other than the paraxial region. Each surface of the first lens 310 to the eighth lens 380 may have an aspherical coefficient as shown in Table 6. For example, both the object-side surface and the image-side surface of the first lens 310 to the eighth lens 380 may be aspherical. [Table 6] In addition, the optical imaging system 300 may have the aberration characteristics shown in FIG. 6. The optical imaging system 400 according to the fourth embodiment will be described with reference to FIGS. 7 and 8. The optical imaging system 400 may include an optical system including a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, a sixth lens 460, a seventh lens 470, and an eighth lens 480, and may further include a filter 490 and an image sensor IS. The optical imaging system 400 may form a focus on the imaging plane 491. The imaging plane 491 may refer to a surface on which the optical imaging system can form a focus. For example, the imaging plane 491 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 7. [Table 7] The total focal length f of the optical imaging system 400 may be 6.338 mm, the IMG HT may be 6.12 mm, and the FOV may be 85.3°. In the fourth example, the first lens 410 may have a positive refractive power, the first surface of the first lens 410 may be convex, and the second surface of the first lens 410 may be concave. The second lens 420 may have a negative refractive power, the first surface of the second lens 420 may be convex, and the second surface of the second lens 420 may be concave. The third lens 430 may have a positive refractive power, the first surface of the third lens 430 may be convex, and the second surface of the third lens 430 may be concave. The fourth lens 440 may have a positive refractive power, the first surface of the fourth lens 440 may be concave, and the second surface of the fourth lens 440 may be convex. The fifth lens 450 may have a negative refractive power, the first surface of the fifth lens 450 may be convex, and the second surface of the fifth lens 450 may be concave. The sixth lens 460 may have a negative refractive power, the first surface of the sixth lens 460 may be convex in the paraxial region, and the second surface of the sixth lens 460 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 460. For example, the first surface of the sixth lens 460 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the sixth lens 460 may be concave in the paraxial region and convex in a portion other than the paraxial region. The seventh lens 470 may have a positive refractive power, the first surface of the seventh lens 470 may be convex in the paraxial region, and the second surface of the seventh lens 470 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 470. For example, the first surface of the seventh lens 470 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the seventh lens 470 may be concave in the paraxial region and convex in a portion other than the paraxial region. The eighth lens 480 may have a negative refractive power, the first surface of the eighth lens 480 may be convex, and the second surface of the eighth lens 480 may be concave. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 480. For example, the first surface of the eighth lens 480 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the eighth lens 480 may be concave in the paraxial region and convex in a portion other than the paraxial region. Each surface of the first lens 410 to the eighth lens 480 may have an aspherical coefficient as shown in Table 8. For example, both the object-side surface and the image-side surface of the first lens 410 to the eighth lens 480 may be aspherical. [Table 8] In addition, the optical imaging system 400 may have the aberration characteristics shown in FIG. 8. The optical imaging system 500 according to the fifth example will be described with reference to FIGS. 9 and 10. The optical imaging system 500 may include an optical system including a first lens 510, a second lens 520, a third lens 530, a fourth lens 540, a fifth lens 550, a sixth lens 560, a seventh lens 570, and an eighth lens 580, and may further include a filter 590 and an image sensor IS. The optical imaging system 500 may form a focus on the imaging plane 591. The imaging plane 591 may refer to a surface on which the optical imaging system can form a focus. For example, the imaging plane 591 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 9. [Table 9] The total focal length f of the optical imaging system 500 may be 6.4215 mm, IMG HT may be 6.12 mm, and FOV may be 85.3°. In the fifth example, the first lens 510 may have a positive refractive power, the first surface of the first lens 510 may be convex, and the second surface of the first lens 510 may be concave. The second lens 520 may have a negative refractive power, the first surface of the second lens 520 may be convex, and the second surface of the second lens 520 may be concave. The third lens 530 may have a positive refractive power, the first surface of the third lens 530 may be convex, and the second surface of the third lens 530 may be concave. The fourth lens 540 may have a positive refractive power, the first surface of the fourth lens 540 may be convex, and the second surface of the fourth lens 540 may be concave. The fifth lens 550 may have a negative refractive power, and both the first surface and the second surface of the fifth lens 550 may be concave. The sixth lens 560 may have a negative refractive power, the first surface of the sixth lens 560 may be convex in the paraxial region, and the second surface of the sixth lens 560 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 560. For example, the first surface of the sixth lens 560 may be convex in the paraxial region and concave in portions other than the paraxial region. The second surface of the sixth lens 560 may be concave in the paraxial region and convex in portions other than the paraxial region. The seventh lens 570 may have a positive refractive power, and both the first surface and the second surface of the seventh lens 570 may be convex in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 570. For example, the first surface of the seventh lens 570 may be convex in the paraxial region and concave in portions other than the paraxial region. The second surface of the seventh lens 570 may be convex in the paraxial region and concave in portions other than the paraxial region. The eighth lens 580 may have a negative refractive power, and both the first surface and the second surface of the eighth lens 580 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 580. For example, the first surface of the eighth lens 580 may be convex in the paraxial region and concave in portions other than the paraxial region. The second surface of the eighth lens 580 may be concave in the paraxial region and convex in portions other than the paraxial region. Each surface of the first lens 510 to the eighth lens 580 may have an aspherical coefficient as shown in Table 10. For example, both the object-side surface and the image-side surface of the first lens 510 to the eighth lens 580 may be aspherical. [Table 10] In addition, the optical imaging system 500 may have the aberration characteristics shown in FIG. 10. The optical imaging system 600 according to the sixth example will be described with reference to FIGS. 11 and 12. The optical imaging system 600 may include an optical system including a first lens 610, a second lens 620, a third lens 630, a fourth lens 640, a fifth lens 650, a sixth lens 660, a seventh lens 670, and an eighth lens 680, and may further include a filter 690 and an image sensor IS. The optical imaging system 600 may form a focal point on the imaging plane 691. The imaging plane 691 may refer to a surface on which the optical imaging system can form a focal point. For example, the imaging plane 691 may refer to a surface of the image sensor IS on which light is received. List the lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens in Table 11. [Table 11] The total focal length f of the optical imaging system 600 can be 6.2999 mm, the IMG HT can be 6.12 mm, and the FOV can be 85.3°. In the sixth example, the first lens 610 can have a positive refractive power, the first surface of the first lens 610 can be convex, and the second surface of the first lens 610 can be concave. The second lens 620 can have a negative refractive power, the first surface of the second lens 620 can be convex, and the second surface of the second lens 620 can be concave. The third lens 630 can have a negative refractive power, the first surface of the third lens 630 can be convex, and the second surface of the third lens 630 can be concave. The fourth lens 640 can have a positive refractive power, the first surface of the fourth lens 640 can be concave, and the second surface of the fourth lens 640 can be convex. The fifth lens 650 can have a negative refractive power, the first surface of the fifth lens 650 can be convex, and the second surface of the fifth lens 650 can be concave. The sixth lens 660 can have a negative refractive power, the first surface of the sixth lens 660 can be convex in the paraxial region, and the second surface of the sixth lens 660 can be concave in the paraxial region. In addition, at least one inflection point can be formed on at least one of the first surface and the second surface of the sixth lens 660. For example, the first surface of the sixth lens 660 can be convex in the paraxial region and concave in the part other than the paraxial region. The second surface of the sixth lens 660 can be concave in the paraxial region and convex in the part other than the paraxial region. The seventh lens 670 can have a positive refractive power, the first surface of the seventh lens 670 can be convex in the paraxial region, and the second surface of the seventh lens 670 can be concave in the paraxial region. In addition, at least one inflection point can be formed on at least one of the first surface and the second surface of the seventh lens 670. For example, the first surface of the seventh lens 670 can be convex in the paraxial region and concave in the part other than the paraxial region. The second surface of the seventh lens 670 can be concave in the paraxial region and convex in the part other than the paraxial region. The eighth lens 680 can have a negative refractive power, the first surface of the eighth lens 680 can be convex in the paraxial region, and the second surface of the eighth lens 680 can be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 680. For example, the first surface of the eighth lens 680 may be convex in the paraxial region and concave in the portion other than the paraxial region. The second surface of the eighth lens 680 may be concave in the paraxial region and convex in the portion other than the paraxial region. Each surface of the first lens 610 to the eighth lens 680 may have an aspherical coefficient as shown in Table 12. For example, both the object-side surface and the image-side surface of the first lens 610 to the eighth lens 680 may be aspherical. [Table 12] In addition, the optical imaging system 600 may have the aberration characteristics shown in FIG. 12. The optical imaging system 700 according to the seventh example will be described with reference to FIGS. 13 and 14. The optical imaging system 700 may include an optical system including a first lens 710, a second lens 720, a third lens 730, a fourth lens 740, a fifth lens 750, a sixth lens 760, a seventh lens 770, and an eighth lens 780, and may further include a filter 790 and an image sensor IS. The optical imaging system 700 may form a focus on the imaging plane 791. The imaging plane 791 may refer to a surface on which the optical imaging system can form a focus. For example, the imaging plane 791 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 13. [Table 13] The total focal length f of the optical imaging system 700 may be 6.2796 mm, IMG HT may be 6.12 mm, and FOV may be 85.3°. In the seventh example, the first lens 710 may have a positive refractive power, the first surface of the first lens 710 may be convex, and the second surface of the first lens 710 may be concave. The second lens 720 may have a negative refractive power, the first surface of the second lens 720 may be convex, and the second surface of the second lens 720 may be concave. The third lens 730 may have a negative refractive power, the first surface of the third lens 730 may be convex, and the second surface of the third lens 730 may be concave. The fourth lens 740 may have a positive refractive power, and the first surface and the second surface of the fourth lens 740 may be convex. The fifth lens 750 may have a negative refractive power. The first surface of the fifth lens 750 may be convex, and the second surface of the fifth lens 750 may be concave. The sixth lens 760 may have a negative refractive power. The first surface of the sixth lens 760 may be convex in the paraxial region, and the second surface of the sixth lens 760 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 760. For example, the first surface of the sixth lens 760 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the sixth lens 760 may be concave in the paraxial region and convex in a portion other than the paraxial region. The seventh lens 770 may have a positive refractive power. The first surface of the seventh lens 770 may be convex in the paraxial region, and the second surface of the seventh lens 770 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 770. For example, the first surface of the seventh lens 770 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the seventh lens 770 may be concave in the paraxial region and convex in a portion other than the paraxial region. The eighth lens 780 may have a negative refractive power. The first surface of the eighth lens 780 may be convex in the paraxial region, and the second surface of the eighth lens 780 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 780. For example, the first surface of the eighth lens 780 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the eighth lens 780 may be concave in the paraxial region and convex in a portion other than the paraxial region. Each surface of the first lens 710 to the eighth lens 780 may have an aspherical coefficient as shown in Table 14. For example, both the object-side surface and the image-side surface of the first lens 710 to the eighth lens 780 may be aspherical. [Table 14] In addition, the optical imaging system 700 may have the aberration characteristics shown in FIG. 14. The optical imaging system 800 according to the eighth embodiment will be described with reference to FIGS. 15 and 16. The optical imaging system 800 may include an optical system including a first lens 810, a second lens 820, a third lens 830, a fourth lens 840, a fifth lens 850, a sixth lens 860, a seventh lens 870, and an eighth lens 880, and may further include a filter 890 and an image sensor IS. The optical imaging system 800 may form a focus on the imaging plane 891. The imaging plane 891 may refer to a surface on which the optical imaging system can form a focus. For example, the imaging plane 891 may refer to a surface of the image sensor IS on which light is received. The lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, and focal length) of each lens are listed in Table 15. [Table 15] The total focal length f of the optical imaging system 800 may be 6.4236 mm, the IMG HT may be 6.12 mm, and the FOV may be 85.3°. In the eighth example, the first lens 810 may have a positive refractive power, the first surface of the first lens 810 may be convex, and the second surface of the first lens 810 may be concave. The second lens 820 may have a negative refractive power, the first surface of the second lens 820 may be convex, and the second surface of the second lens 820 may be concave. The third lens 830 may have a positive refractive power, the first surface of the third lens 830 may be convex, and the second surface of the third lens 830 may be concave. The fourth lens 840 may have a positive refractive power, the first surface of the fourth lens 840 may be convex, and the second surface of the fourth lens 840 may be concave. The fifth lens 850 may have a negative refractive power, the first surface of the fifth lens 850 may be concave, and the second surface of the fifth lens 850 may be convex. The sixth lens 860 may have a positive refractive power, the first surface of the sixth lens 860 may be convex in the paraxial region, and the second surface of the sixth lens 860 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the sixth lens 860. For example, the first surface of the sixth lens 860 may be convex in the paraxial region and concave in a portion other than the paraxial region. The second surface of the sixth lens 860 may be concave in the paraxial region and convex in a portion other than the paraxial region. The seventh lens 870 may have a positive refractive power, and both the first surface and the second surface of the seventh lens 870 may be convex in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the seventh lens 870. For example, the first surface of the seventh lens 870 may be convex in the paraxial region and concave in the portion other than the paraxial region. The second surface of the seventh lens 870 may be convex in the paraxial region and concave in the portion other than the paraxial region. The eighth lens 880 may have a negative refractive power, and both the first surface and the second surface of the eighth lens 880 may be concave in the paraxial region. In addition, at least one inflection point may be formed on at least one of the first surface and the second surface of the eighth lens 880. For example, the first surface of the eighth lens 880 may be concave in the paraxial region and convex in the portion other than the paraxial region. The second surface of the eighth lens 880 may be concave in the paraxial region and convex in the portion other than the paraxial region. Each surface of the first lens 810 to the eighth lens 880 may have an aspherical coefficient as shown in Table 16. For example, both the object-side surface and the image-side surface of the first lens 810 to the eighth lens 880 may be aspherical. [Table 16] In addition, the optical imaging system 800 may have the aberration characteristics shown in FIG. 16. [Table 17] According to the foregoing examples, the optical imaging system may have a reduced size while implementing high resolution. Although this disclosure includes specific examples, it will be apparent to those of ordinary skill in the art that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples set forth herein should be considered illustrative only and not for limiting purposes. The description of the features or aspects in each example should be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the techniques described are implemented in a different order, and / or if the components in the systems, architectures, devices, or circuits described are combined in a different manner and / or replaced or supplemented by other components or their equivalents. Accordingly, the scope of this disclosure is not defined by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be construed as being included in this disclosure. 100, 200, 300, 400, 500, 600, 700, 800: Optical imaging system 110, 210, 310, 410, 510, 610, 710, 810: First lens 120, 220, 320, 420, 520, 620, 720, 820: Second lens 130, 230, 330, 430, 530, 630, 730, 830: Third lens 140, 240, 340, 440, 540, 640, 740, 840: Fourth lens 150, 250, 350, 450, 550, 650, 750, 850: Fifth lens 160, 260, 360, 460, 560, 660, 760, 860: Sixth lens 170, 270, 370, 470, 570, 670, 770, 870: Seventh lens 180, 280, 380, 480, 580, 680, 780, 880: Eighth lens 190, 290, 390, 490, 590, 690, 790, 890: Filter 191, 291, 391, 491, 591, 691, 791, 891: Imaging plane IS: Image sensor FIG. 1 is a diagram showing an optical imaging system according to a first example. FIG. 2 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 1. FIG. 3 is a diagram showing an optical imaging system according to a second example. FIG. 4 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 3. FIG. 5 is a diagram showing an optical imaging system according to a third example. FIG. 6 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 5. FIG. 7 is a diagram showing an optical imaging system according to a fourth example. FIG. 8 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 7. FIG. 9 is a diagram showing an optical imaging system according to a fifth example. FIG. 10 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 9. FIG. 11 is a diagram showing an optical imaging system according to a sixth example. FIG. 12 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 11. FIG. 13 is a diagram showing an optical imaging system according to a seventh example. FIG. 14 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 13. FIG. 15 is a diagram showing an optical imaging system according to an eighth example. FIG. 16 is a curve indicating the aberration properties of the optical imaging system shown in FIG. 15. Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be drawn to scale, and for clarity, illustration, and convenience, the relative sizes, proportions, and illustrations of the elements in the drawings may be exaggerated. 100: Optical imaging system 110: First lens 120: Second lens 130: Third lens 140: Fourth lens 150: Fifth lens 160: Sixth lens 170: Seventh lens 180: Eighth lens 190: Filter 191: Imaging plane IS: Image sensor

Claims

1. An optical imaging system, comprising: The first lens has a positive refractive power; the second lens has a negative refractive power. The third lens has refractive power; the fourth lens has positive refractive power. The fifth lens has a negative refractive power; the sixth lens has a refractive power; the seventh lens has a positive refractive power; and the eighth lens has a negative refractive power, wherein the first lens to the eighth lens are arranged sequentially from the object side, and the optical imaging system has a total of eight lenses, wherein 25 < v1-v2 < 45; 0 < |f2 / f3| < 1; 3 < |f4 / f|; and 0 < f7 / f < 2, where v1 is the Abbe number of the first lens, v2 is the Abbe number of the second lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f7 is the focal length of the seventh lens, and f is the total focal length of the optical imaging system, and each of the second and fifth lenses has a refractive index greater than 1.

66.

2. The optical imaging system of claim 1, wherein at least three lenses, including the second lens, among the first to the eighth lenses have a refractive index greater than 1.61, and wherein among the at least three lenses with a refractive index greater than 1.61, the second lens has the smallest absolute value of focal length.

3. The optical imaging system as claimed in claim 1, wherein v1-v4 < 45, where v4 is the Abbe number of the fourth lens.

4. The optical imaging system as claimed in claim 1, wherein 60 < v2 + v5 + v6 < 80, where v5 is the Abbe number of the fifth lens and v6 is the Abbe number of the sixth lens.

5. The optical imaging system as claimed in claim 1, wherein 0 < f1 / f < 1.4, and f1 is the focal length of the first lens.

6. The optical imaging system as claimed in claim 1, wherein at least one of the following is satisfied: -10 < f2 / f < -1; and 1 < |f3 / f|.

7. The optical imaging system as claimed in claim 1, wherein -0.6 < f1 / f2 < 0, and f1 is the focal length of the first lens.

8. The optical imaging system as claimed in claim 1, wherein 3 < |f5 / f|, where f5 is the focal length of the fifth lens.

9. The optical imaging system as claimed in claim 1, wherein 1 < |f6 / f|, where f6 is the focal length of the sixth lens.

10. The optical imaging system as claimed in claim 1, wherein -1 < f8 / f < 0, and f8 is the focal length of the eighth lens.

11. The optical imaging system of claim 1, wherein TTL / f < 1.3 and BFL / f < 0.3, wherein TTL is the distance along the optical axis from the object-side surface of the first lens to the imaging plane and BFL is the distance along the optical axis from the image-side surface of the eighth lens to the imaging plane.

12. The optical imaging system of claim 1, wherein 0 < D1 / f < 0.1, and D1 is the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens.

13. The optical imaging system of claim 1, wherein 70° < FOV × (IMG HT / f), where FOV is the field of view of the optical imaging system and IMG HT is half the diagonal length of the imaging plane.

14. The optical imaging system as claimed in claim 1, wherein the third lens has a negative refractive power.

15. The optical imaging system as claimed in claim 1, wherein the sixth lens has a negative refractive power.

16. The optical imaging system as claimed in claim 1, wherein, The first lens has a convex object-side surface and a concave image-side surface in the paraxial region, the second lens has a convex object-side surface and a concave image-side surface in the paraxial region, and the third lens has a convex object-side surface and a concave image-side surface in the paraxial region.

17. The optical imaging system as claimed in claim 1, wherein, The fifth lens has a convex object-side surface and a concave image-side surface in the paraxial region, the seventh lens has a convex object-side surface and a concave image-side surface in the paraxial region, and the eighth lens has a convex object-side surface and a concave image-side surface in the paraxial region.

18. The optical imaging system as claimed in claim 1, wherein, The fourth lens has a convex object-side surface and a concave image-side surface in the paraxial region.

19. The optical imaging system as claimed in claim 1, wherein, The sixth lens has a concave image-side surface in the paraxial region.

Images